Tuesday, January 20, 2009

Dragon as the new CRV?

In my previous post (A more gentle transition) I tossed out an idea that perhaps a Dragon capsule, launched to the station in support of ISS logistics, could be modified to serve as a crew lifeboat while it is docked to the station. I was quite surprised, then, to stumble across this post (The new X-38/CRV: SpaceX's Dragon?) by Rob Coppinger yesterday, which references this article (Race to the International Space Station begins in earnest) by John Croft over at Flight Global.

I had no idea if such a thing was possible; only that it would make sense to try and use the Dragon for ISS crew-return if dealing with the Russians proved to be problematic in the future. Using the Dragon this way would also remove one of the frequently cited reasons why the Shuttle should not be used to service the ISS beyond 2010; namely that it could not remain docked to the ISS for extended periods of time, and thus could not be used as an ISS lifeboat. But if this story is correct, then there are already studies underway to validate this concept.

The primary difference between this report and my hypothetical scenario is that they appear to be studying the prospect of delivering the Dragon capsule in the payload bay of the Space Shuttle. I guess I assumed that the Falcon 9 would have successfully flown by the time this would be needed. I cannot think of any other reason why they would rather use the Shuttle. If Falcon 9 has been successfully flown by 2010, then it would certainly be cheaper to launch the capsule to the station using a Falcon 9; not to mention the fact that the Dragon is designed to be launched by a Falcon 9.

My other assumption regarding how it might be easy to temporarily convert a cargo Dragon into a CRV while it is docked to the station, may have also been a little too optimistic. There are probably alot of sub-systems that would be present in a crewed Dragon (even a minimal reentry version), that would probably not be found on an unmanned cargo Dragon. If absolutely necessary, a crew could probably ride down like cargo; however, they would most likely want a more robust life-support capacity and manual flight controls available in an actual CRV Dragon.

I have just one more idea, that I'd like to throw out there. I've been thinking for some time now that NASA should get a Sundancer class module from Bigelow and launch it into an orbit near the Hubble space telescope. That way, if anything goes wrong with the STS-125 mission, they would at least have the opportunity to use the module as a safe haven until a rescue mission can be mounted.

Now, there may be another way to add crew rescue capability to STS-125. If they are actually studying the feasibility of launching the Dragon on the Shuttle, then perhaps it would be possible to tuck one away in the back of the payload bay for the Hubble repair mission. Would there be room? Would the Dragon be ready in time? My guess is: probably not, but it's an interesting idea none-the-less.

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Blogger windbourne said...

Hmmm. Love the idea of the sundancer for emergency.
I have been thinking for quite some time that Bigelow would do well to get one up on the ISS. There are already several smaller ones in orbit. Allow it to hold cargo, or better yet, just let it serve for the crew quarters. One of the issues with the current ISS is that it is LOUD. I would expect the bigelow to absorb sound. Then when a BA-330 comes along, add one to the ISS as well (or replace the sundancer). Using a delta or one of the falcon 9's to attach one to the ISS would also boost Bigelow and get them moving forward.

10:58 PM, January 20, 2009  
Blogger Eric M. Collins said...

You'd think that NASA would jump all over the chance to install some extra habitable volume to the ISS. The modules are based largely on NASA's transhab design, which would have been tested out on the ISS prior to it being used for a trips to Mars. Unfortunately, I've not heard any rumors about NASA being interested in any Bigelow modules for the ISS.

5:36 AM, January 22, 2009  
Anonymous Dean Crockett said...

The ISS and the Hubble are in profoundly different orbits. There is no way to park a habitation module near the Hubble and have it accessable by the ISS crew. It would take less delta-v to de-orbit the crew in an emergency than it would to get them into an emergency module near the Hubble. Other than that, it's not a bad idea to park other/future habitable modules (Bigelow, et. al.) in the same orbit, a few degrees ahead/behind the ISS. That way, if anyone is in trouble in one settlement they can get to the other settlement easily. Even this, though, is harder than it probably seems. The ISS is in such a low orbit that it is constantly decaying and needs to be boosted by the Shuttle when it visits. Every habitation in orbit "near" the ISS would need to go through similar evolutions at about the same frequency in order to stay nearby. Orbital mechanics are non-trivial exercises in reality. But all-in-all I think that it's a good idea to have multiple settlements in the same general orbit so that the inhabitants can reach eachother for commerce or in emergencies.

11:09 AM, February 12, 2009  
Blogger Eric M. Collins said...

You are correct, the STS-125 mission to Hubble will not be able to use the ISS, or anything in its orbit, as a safe haven. I was, therefore, suggesting that they put a Bigelow habitat up in an orbit near the Hubble telescope. In the event that they make it to orbit but cannot come back down, they would rendezvous with the fully provisioned habitat and be able to wait for a rescue mission to be launched.

I had this idea a couple of years ago when they started talking about doing a Hubble repair mission without the prospect of being able to take refuge at the ISS. I'm not sure where Bigelow Aerospace is at the moment with regards to the development of their first habitable module, but it's probably not likely that they will have it ready in time to be used for the upcoming STS-125 mission.

Having a Dragon capsule in the payload bay would be like having an escape pod on board. Unfortunately, I don't think they will have room for it on this mission, nor do I think it would be particularly wise to rely on an untested vehicle for crew rescue. I guess the same thing applies to the Bigelow habitat.

8:06 AM, February 13, 2009  

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